Hi Alex, Hope for some suggestions or comments from you since there seems to be many unsure points in this series. :-) Thanks, Shenming On 2021/4/26 9:41, Shenming Lu wrote: > On 2021/4/9 11:44, Shenming Lu wrote: >> Hi, >> >> Requesting for your comments and suggestions. :-) > > Kind ping... > >> >> The static pinning and mapping problem in VFIO and possible solutions >> have been discussed a lot [1, 2]. One of the solutions is to add I/O >> Page Fault support for VFIO devices. Different from those relatively >> complicated software approaches such as presenting a vIOMMU that provides >> the DMA buffer information (might include para-virtualized optimizations), >> IOPF mainly depends on the hardware faulting capability, such as the PCIe >> PRI extension or Arm SMMU stall model. What's more, the IOPF support in >> the IOMMU driver has already been implemented in SVA [3]. So we add IOPF >> support for VFIO passthrough based on the IOPF part of SVA in this series. >> >> We have measured its performance with UADK [4] (passthrough an accelerator >> to a VM(1U16G)) on Hisilicon Kunpeng920 board (and compared with host SVA): >> >> Run hisi_sec_test... >> - with varying sending times and message lengths >> - with/without IOPF enabled (speed slowdown) >> >> when msg_len = 1MB (and PREMAP_LEN (in Patch 4) = 1): >> slowdown (num of faults) >> times VFIO IOPF host SVA >> 1 63.4% (518) 82.8% (512) >> 100 22.9% (1058) 47.9% (1024) >> 1000 2.6% (1071) 8.5% (1024) >> >> when msg_len = 10MB (and PREMAP_LEN = 512): >> slowdown (num of faults) >> times VFIO IOPF >> 1 32.6% (13) >> 100 3.5% (26) >> 1000 1.6% (26) >> >> History: >> >> v2 -> v3 >> - Nit fixes. >> - No reason to disable reporting the unrecoverable faults. (baolu) >> - Maintain a global IOPF enabled group list. >> - Split the pre-mapping optimization to be a separate patch. >> - Add selective faulting support (use vfio_pin_pages to indicate the >> non-faultable scope and add a new struct vfio_range to record it, >> untested). (Kevin) >> >> v1 -> v2 >> - Numerous improvements following the suggestions. Thanks a lot to all >> of you. >> >> Note that PRI is not supported at the moment since there is no hardware. >> >> Links: >> [1] Lesokhin I, et al. Page Fault Support for Network Controllers. In ASPLOS, >> 2016. >> [2] Tian K, et al. coIOMMU: A Virtual IOMMU with Cooperative DMA Buffer Tracking >> for Efficient Memory Management in Direct I/O. In USENIX ATC, 2020. >> [3] https://patchwork.kernel.org/project/linux-arm-kernel/cover/20210401154718.307519-1-jean-philippe@xxxxxxxxxx/ >> [4] https://github.com/Linaro/uadk >> >> Thanks, >> Shenming >> >> >> Shenming Lu (8): >> iommu: Evolve the device fault reporting framework >> vfio/type1: Add a page fault handler >> vfio/type1: Add an MMU notifier to avoid pinning >> vfio/type1: Pre-map more pages than requested in the IOPF handling >> vfio/type1: VFIO_IOMMU_ENABLE_IOPF >> vfio/type1: No need to statically pin and map if IOPF enabled >> vfio/type1: Add selective DMA faulting support >> vfio: Add nested IOPF support >> >> .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 3 +- >> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 18 +- >> drivers/iommu/iommu.c | 56 +- >> drivers/vfio/vfio.c | 85 +- >> drivers/vfio/vfio_iommu_type1.c | 1000 ++++++++++++++++- >> include/linux/iommu.h | 19 +- >> include/linux/vfio.h | 13 + >> include/uapi/linux/iommu.h | 4 + >> include/uapi/linux/vfio.h | 6 + >> 9 files changed, 1181 insertions(+), 23 deletions(-) >>
